AN ORDINANCE relating to The City of Seattle’s datum point; updating the vertical and horizontal reference datum for City of Seattle departments and outside entities as a standard elevation reference plane; requiring certain measurements for preliminary plats to be based on the updated vertical and horizontal datum; amending Chapter 1.20 of the Seattle Municipal Code; and amending Sections 23.22.020, 23.75.100, 25.06.030, 25.06.070, and 25.06.090 of the Seattle Municipal Code.